A capacity of a WCDMA (Wideband Code Division Multiple Access) system is limited by a downlink capacity; in view of this, a technology such as HSDPA (High Speed Downlink Packet Access) is introduced to WCDMA R5 (Wideband Code Division Multiple Access Release 5), thereby implementing high-speed downlink data transmission. However, in an HSDPA environment, a soft handover cannot be performed on UE (user equipment). Therefore, an MF (multiflow transmission) technology is introduced again, that is, in a soft handover area, multiple links may be configured for UE of HSDPA to send data. After an MF-HSDPA feature is applied, downlink throughput performance of the UE in the soft handover area can be improved, and network resource utilization is also improved. For the MF technology, currently, there may be multiple modes according to a quantity of frequencies and a quantity of cells: an SF-DC (single frequency-dual cell) mode, a DF-3C (dual frequency-three cells) mode, a DF-4C (dual frequency-four cells) mode, and the like. When a dual-frequency or multiple-frequency mode such as the DF-3C mode is used, the UE can receive downlink data simultaneously in cells on two or multiple frequencies, but the UE performs uplink feedback in a joint coding manner only on a primary frequency. In addition, a DC-HSDPA (dual-carrier High Speed Downlink Packet Access) feature is also introduced, and the UE can receive downlink data on two frequencies simultaneously if there are two inter-frequency co-coverage cells.
With the development of mobile communications technologies, users have increasingly higher requirements. A small cell is introduced to an existing macro network, so that a quantity of system cells can multiply. If a throughput of each cell remains unchanged, a system capacity may multiply (or even increase tenfold). A Hetnet (heterogeneous network) is formed after a small cell is introduced to a macro cell. A small-cell base station may include a home base station, or referred to as a femtocell, an AP (access point), a Pico (a picocell base station), and a Micro (a micro base station).
The introduction of a small-cell base station may have the following advantages: a coverage range is relatively small; a network device cost (small-scale integration), a network deployment cost (a site may not be needed), and a network transmission cost (an IP network may be used) are reduced; a network operation cost is reduced, where for a Small Cell in the Hetnet, contiguous coverage is not needed, and a small amount of planning and automatic network optimization may be achieved based on a SON (self-organizing network) feature; energy is conserved and radiation is low (transmit power of some Small Cells may be lower than transmit power of UE). The small-cell base station is applicable in a wide range of scenarios, such as a home scenario, an enterprise scenario, or a public place scenario; especially, in the scenarios, such as the enterprises scenario and the public place scenario, in which multiple small-cell base stations are needed for continuous networking, the introduction of the small-cell base station is aimed at enhancing coverage of these scenarios, and can also help the macro cell perform service offloading.
For example, in a networking scenario shown in FIG. 1, a serving HS-DSCH cell (serving high speed downlink shared channel cell) of UE is a Cell 1 on a frequency F1. At a point A, a configuration of the UE is DC-HSDPA. When the UE moves from the point A to a point B (a dashed line with an arrow in FIG. 1 indicates a direction of movement of the UE), a Cell 3 interferes with a Cell 2, where the Cell 3 and the Cell 2 are both on a frequency F2, causing that a link of the Cell 2 becomes worse, thereby affecting a throughput of the UE and user experience; at this time, the Cell 3 should be configured for the UE to perform a multiflow transmission operation.
In the scenario shown in FIG. 1, 1x events, such as a is event, a 1b event, a is event, and a 1d event, for measurement of a cell need to be reported. The 1x events are mainly used to maintain intra-frequency cell measurement and event reporting, mainly aimed at reporting for a cell; for example, the 1d event indicates that a current best cell changes. To report a 1x event, one best cell (best cell) needs to be initialized first, where the cell is a cell having the best measurement signal in an active set, and information about the best cell is stored in a 1d event variable BEST_CELL_1D_EVENT (which is also indicated by TRIGGERED_1D_EVENT sometimes) of the UE; a subsequently measured cell is compared with the cell; if the subsequently measured cell is better than the cell, the UE is triggered to report a 1d event, and a handover between downlink serving cells is triggered on a network side according to the 1d event reported by the UE. A 2x event is mainly aimed at inter-frequency measurement, used to estimate signal quality of all measured cells on a frequency, and is mainly applied to the frequency. For the scenario in FIG. 1, obviously, the UE needs to report a 1x event, especially, a 1d event to enable a network to find the cell 3 and to perform a subsequent operation, such as an operation of changing the serving HS-DSCH cell of the UE to the cell 3, configuring the UE to perform a DF-3C operation, or configuring an SF-DC operation on the frequency F2.
Currently, a DC-HSUPA (dual-carrier High Speed Downlink Packet Access) feature has been introduced, and the UE may send uplink data in two inter-frequency cells. This feature already supports a case in which the UE can use a cell on a secondary (second) frequency as an intra-frequency cell to perform intra-frequency measurement and report 1x events, such as a 1a event, a 1b event, and a 1c event; however, this feature does not support reporting of a 1d event. This is because cells on a primary frequency and a secondary frequency appear in pairs, a 1d event on the secondary frequency is not needed for triggering a handover between downlink serving cells, and only a 1d event on the primary frequency is needed. However, macro and small cells in a Hetnet scenario are not co-coverage cells, that is, the macro and small cells do not appear in pairs, and therefore reporting of a 1d event needs to be supported. If a 1x event needs to be reported, an active set needs to be maintained, which requires all cells in the active set to be related to a soft handover, that is, uplink and downlink links need to be configured for all related cells in a UE active set; if a DC-HSUPA operation meets this condition, the UE simultaneously establishes uplink and downlink links in cells on the secondary frequency. When only an HSDPA-related operation, such as a DC-HSDPA operation, a DF-3C (dual frequency-three cells) operation, or a DF-4C (dual frequency-four cells) operation, is configured, and only a channel related to downlink data transmission, such as an HS-SCCH (high speed shared control channel) or an HS-PDSCH (high speed physical downlink shared channel), is configured on the secondary (second) frequency (such as the frequency F2 in FIG. 1), but a channel such as a DPCH (dedicated physical channel) is not configured, these cells are inconsistent with a definition of an active set, and uplink and downlink data cannot be transmitted simultaneously.
That is, in the scenario shown in FIG. 1, on the secondary frequency, there is only downlink data and only one serving cell of serving HS-DSCH cell, an active set cannot be maintained, and the UE cannot initialize information about one best cell and therefore cannot subsequently compare information about another cell with the information about the best cell; as a result, the UE cannot report, on the secondary frequency, a 1d event for a cell.